Online work marketplaces help clients and contractors across the globe to connect with each other and work for more than $1 billion in annual contractor earnings just in the year 2014. Typically, in such marketplaces, contractors apply to jobs posted by clients and clients hire applicant(s) that seems to be the best fit for the jobs posted. As their platforms grow, a fundamental problem that the marketplaces have to solve is the understanding of successful client hiring practices such that the marketplaces can help clients make the right hiring decisions. Without such help, clients will have to deal with the friction of screening tens to hundreds of contractors to determine the ideal candidates for their jobs. The screening process is not only time consuming, but it is also error-prone since clients often lack the necessary knowledge to assess the qualifications of contractors (e.g., education and work experience from schools and companies that are unknown to a client). Understanding and modeling the hiring behavior of clients is challenging not only due to the variety of jobs that are posted and the diversity of contractors, but also due to the heterogeneity of client hiring criteria.